The diagnosis and treatment of patients with cancerous tumors, pre-malignant conditions, and other disorders has long been an area of intense investigation. Non-invasive methods for examining tissue are palpation, X-ray, MRI, CT, and ultrasound imaging. When the physician suspects that a tissue may contain cancerous cells, a biopsy may be done either in an open procedure or in a percutaneous procedure. For an open procedure, a scalpel is used by the surgeon to create a large incision in the tissue in order to provide direct viewing and access to the tissue mass of interest. Removal of the entire mass (excisional biopsy) or a part of the mass (incisional biopsy) is done. For a percutaneous biopsy, a needle-like instrument is used through a very small incision to access the tissue mass of interest and to obtain a tissue sample for later examination and analysis. The advantages of the percutaneous method as compared to the open method are significant: less recovery time for the patient, less pain, less surgical time, lower cost, less risk of injury to adjacent bodily tissues such as nerves, and less disfigurement of the patient's anatomy. Use of the percutaneous method in combination with artificial imaging devices such as X-ray and ultrasound has resulted in highly reliable diagnoses and treatments.
Generally there are two ways to obtain percutaneously a portion of tissue from within the body, by aspiration or by core sampling. Aspiration of the tissue through a fine needle requires the tissue to be fragmented into small enough pieces to be withdrawn in a fluid medium. The method is less intrusive than other known sampling techniques, but one can only examine cells in the liquid (cytology) and not the cells and the structure (pathology). In core biopsy, a core or fragment of tissue is obtained for histologic examination which may be done via a frozen or paraffin section.
The type of biopsy used depends mainly on various factors present in the patient, and no single procedure is ideal for all cases. Core biopsy, however, is very useful in a number of conditions and is widely used by physicians.
Due largely to heightened public awareness of the need to detect breast cancer early in its development, a number of biopsy devices for use in combination with artificial imaging devices have been commercialized. One such instrument type of biopsy instrument is the BIOPTY gun, available from C.R. Bard, Inc. and described in U.S. Pat. Nos. 4,699,154 and 4,944,308 as well as in U.S. Reissued Pat. No. 34,056. This device is spring-powered and each time a sample is to be taken, the breast or organ must be punctured again upon reinsertion of the device. Another product is the TRUE CUT needle manufactured by Travenol Laboratories. This needle collects a single core of tissue using a pointed stillete with a side-facing notch to receive tissue near its distal end and an outer, sharpened sliding cannula.
Other devices for obtaining biopsy samples from the body are described in the following: U.S. Pat. No. 5,492,130 issued to Chiou on Feb. 20, 1996; U.S. Pat. No. 5,526,821 issued to Jamshidi on Jun. 18, 1996; U.S. Pat. No. 5,429,138 issue to Jamshidi on Jul. 4, 1995; and U.S. Pat. No. 5,027,827 issued to Cody, et al, on Jul. 2, 1991. These patents describe devices which may be used for soft tissue biopsies using the aspiration method of liquid suspended tissue extraction rather than by core sampling. Numerous other devices are described in the references cited in this disclosure, and generally are for the mere removal of tissue rather than the sampling of tissue for later pathological examination.
To overcome operator error associated with such devices, and to enable multiple sampling of the tissue without having to reenter the tissue for each sample, a product now marketed under the tradename MAMMOTOME was developed. The invention which is the basis of the commercialized product is described in U.S. Pat. No. 5,526,822 issued to Burbank, et al, on Jun. 18, 1996, and is commonly owned by the assignee of the present invention. The MAMMOTOME instrument is a type of image-guided, percutaneous, coring, breast biopsy instrument. It is vacuum-assisted and some of the steps for retrieving the tissue samples have been automated. The physician uses this device to capture "actively" (using the vacuum) the tissue prior to severing it from the body. This allows for sampling tissues of varying hardness. The device can also be used to collect multiple samples in numerous positions about its longitudinal axis, and without needing to remove the device from the body. These features allow for substantial sampling of large lesions and complete removal of small ones.
Co-pending application Ser. No. 08/825,899 is a continuation-in-part of the '822 Burbank patent discussed above and describes numerous improvements to the original invention including the following: a molded tissue cassette housing permitting the handling and viewing of multiple tissue samples without physical contact by the instrument operator; the interconnection of the housing to the piercing needle using a thumbwheel to permit the needle to rotate relative to the housing, thereby preventing the vacuum tube from wrapping about the housing; several variant vacuum port embodiments; and a method for backflushing biological debris from the instrument without removing the instrument from the selected tissue location.
When using any of the devices described thus far there is a need to manage a substantial amount of different fluids either already present at the surgical site or introduced during the surgical procedure. There is some associated bleeding from the surgical site during insertion of the needle and severing of the tissue samples from the tissue mass of interest. In addition, several milliliters of local anesthetic such as lidocaine hydrochloride solution are injected into the tissue during the procedure, and there is a significant build-up of pressure inside the tissue due to the presence of the additional fluid. When the blood and anesthetic solution under this pressure within the tissue are opened to a lower or ambient pressure, the fluids will readily escape the tissue at the opening. Keeping these fluids from contaminating the patient and the instrumentation is obviously an important part of the mandatory aseptic technique, and features on the biopsy device to help accomplish this are clearly advantageous.
Coring breast biopsy devices typically incorporate an elongated piercing element to access the sampling area of the tissue mass, and a cutting cannula with a sharpened end which slides longitudinally along the piercing element. The sharpened end of the cutting cannula is driven into the tissue mass, and a core sample of the tissue is captured into the distal end of the cannula. The piercing element and/or the cannula are then withdrawn from the body and, in the case of the MAMMOTOME breast biopsy instrument, the tissue sample is transported and removed from the distal end of the cannula. This is an opportunity for fluids to escape from the tissue mass. The situation is especially acute should the biopsy device be tilted during the step of sample retrieval, as often occurs when the biopsy device is mounted on certain imaging devices. The fluids then will tend to flow "downhill" onto the devices and the surroundings.
Accordingly, what is needed is a biopsy device which can catch the fluids present during a biopsy procedure before they spill on the surroundings, and drain the fluids away to a collection cannister or the like. In addition to dealing with the backflow and gravitational effects already described, the physician also must contend with the fluids being spread by the pumping action of the relatively sliding components of the biopsy device. What is also needed, therefore, are seals advantageously mounted between the sliding components to block the spread of the fluids and to wipe the interacting surfaces clean as the device is actuated.
In the MAMMOTOME device a knockout tube is provided so that as the cutting cannula is withdrawn from the tissue and the distal end of the tube is outside the patient's body, the distal end of the knockout tube pushes out the core sample automatically from the distal end of the cutting cannula. A drain line is attached to the proximal end of the knockout tube so that fluids contained in the cutting cannula can be removed. This drain line may be attached to a vacuum source to remove the fluids more effectively. Sometimes the surgeon wishes to disconnect the drain line from the knockout tube in order to inject an additional amount of anesthetic solution into the tissue mass to insure that a sufficient amount is present at the area where the tissue sample will be taken. By removing this drain line, the fluid within the tissue which may be at a relatively high pressure can escape from the device. What is further needed, therefore, is a connecting valve on the device to allow the disconnection of the drain line, the injection of the anesthetic solution, and the reattachment of the drain line, without the loss of fluids from the tissue and onto the external surroundings. This connecting valve would also be an improvement to biopsy devices which do not have a knockout tube, but which instead have a drain line attached to the proximal end of the cutting cannula or to the proximal end of the piercing element.